To study the influence of bulb preposed or postposed on bulb turbine’s hydraulic performance, which is characterized with microhead, a bulb turbine with design head of approximately one meter has been simulated with threedimensional numerical simulation using CFD software. In addition, the optimal scheme has been tested by considering a physical model. The results show that the head loss of inlet conduit with preposed bulb is slightly larger than postposed bulb, while the head loss of outlet conduit with postposed bulb is much larger than preposed bulb which is due to the reflow in outlet conduit. The reflow can be improved by optimizing the outlet conduit, but cannot be completely eliminated. Bulb preposed or postposed has little influence on the flow in runner. The additional guide vanes in preposed bulb turbine improve the flow pattern on inlet side of runner blade, but cause much larger head loss. The preposed bulb turbine without guide vanes has a simpler structure, a higher efficiency, lower cost and stable operation, and is suitable to the development of micro head water resources. The errors do not exceed 3％ by comparing the efficiency of optimal scheme numerical simulation and model test results, which indicates the accuracy of numerical simulation.